Elemental sulfur (in a variety of forms), sulfides, sulfites and/or mercaptans are commonly used ingredients in dermatologic or cosmetic compositions for the treatment of a variety of dermatological conditions. Various forms of sulfur, sulfides, sulfites and mercaptans are believed to have anti-microbial, anti-fungal, anti-parasitic and anti-inflammatory functions. Sulfur, in its various forms, sulfides, sulfites and mercaptans are believed to kill parasites, such as mites, and microorganisms, including but not limited to bacteria, and thereby also suppress their endotoxins and exotoxins, all of which can be irritants that may contribute to the provocation of itching, redness and irritation that are characteristics of rosacea. Further, sulfur causes keratolytic/sloughing activity and may, therefore, remove irritants that are held by the sloughed cells, as well as smoothing and soothing the skin.
Unfortunately, sulfur containing compositions may be, or may become, malodorous over time yielding a characteristic “rotten egg odor.” This malodor is believed to be caused by the formation of volatile sulfur-containing compounds, for example, hydrogen sulfide (H2S), sulfur dioxide (SO2) and various other volatile sulfides and mercaptans. These odor causing compounds can be generated even by sulfur compounds which are not themselves odor causing. As a result of the unpleasant odor, patients are sometimes reluctant to apply such compositions directed by their physician or pharmacist. Such poor patient compliance can seriously diminish the effectiveness of a treatment regimen.
The prior art has used a variety of techniques to try to deal with the odor associated with sulfur containing compositions. For example, U.S. Pat. No. 4,338,301 describes the use of clays to control the odor of alkaline sulfur containing compositions. Another approach to odor content is to include compounds that react ionically or covalently with odor causing sulfur compounds to reduce or eliminate offensive odors. Examples of agents that can tie-up volatile compounds, such as SO2, H2S, —SH compound, sulfur include heavy metal oxide and related compounds such as zinc oxide, titanium oxide that can form non-volatile or weakly volatile sulfides such as Zinc sulfide, or telamursulfide and the like. Other approaches include the use of scents or perfume to overpower or mask the offensive odor. Sometimes, formulators forgo the use of particular sulfur compounds that generate strong odors, even though they are otherwise desirable. None of these techniques have been entirely satisfactory.
Accordingly, there is a need for improved methods for reducing, inhibiting or eliminating the production of sulfurous malodor in sulfur containing dermatological or cosmetic compositions.